Fiber optic couplers are multiport devices used between fibers or between fibers and solid state detectors and emitters. Applications which use such couplers include multiplexers for combining plural wavelengths into a single fiber and demultiplexers for separating plural wavelengths in a single fiber into distinct fibers or detectors. Couplers are also used for bidirectional coupling between a fiber and a respective detector and emitter.
In all these applications couplers are required which minimize losses, are relatively inexpensive to produce and can be used in the field with success. To insure that losses are minimized, great accuracy is required in the placement of fiber terminations, detectors and emitters and the focus of light paths through the coupler between these elements. Owing to the need for high accuracy in coupler positioning and the complexity of the coupler functions, low cost production is difficult to achieve. Molds for efficient mass production may require side actions which increases cost, slows production and impedes accuracy in the overall coupler element placement. Field utilization of such couplers requires that they be made to be used by lesser trained personnel while avoiding the opportunity for misalignment of the fibers, detectors and emitters that are used with the coupler.
In repeater functions, the light in a fiber is periodically amplified. For this purpose, a fiber is connected to a detector to sense the light signal in the fiber and, after amplification, the light is applied to a further length of fiber through an emitter and connector. Any failure of this system will terminate the transmission of all light along the fiber, causing a complete loss of all signal on the fiber path from that point on.